From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Miller <davem@davemloft.net>
Subject: Re: [PATCH v3] netlink: fix null pointer dereference on nlk->groups
Date: Tue, 12 Jan 2016 14:40:49 -0500 (EST)
Message-ID: <20160112.144049.336054136817784262.davem@davemloft.net>
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From: Baozeng Ding <sploving1@gmail.com>
Date: Tue, 12 Jan 2016 19:10:43 +0800

> If groups is not 0 and nlk->groups is NULL, it will not return
> immediately and cause a null pointer dereference later.
> 
> Signed-off-by: Baozeng Ding <sploving1@gmail.com>
> ---
> The v3 version adds WARN_ON, suggested by David Miller. Thanks for
> David's feedback.

My feedback was also that the situation is illegal, and therefore you
have to explain to us how this can actually occur.